538 PHYSIOLOGY CHAP. 



conspicuously differentiated structure (hetrrotypical formations), 

 coincide with, or are directly related to, the regions whose functions 

 are known from experimental physiological research or clinical 

 observations. These areas are especially : the giganto-pyramidal 

 area (field 4 of Brodmann) characterised by the presence of giant 

 pyramidal cells (Fig. 272), which occupies the precentral region 

 and coincides as we shall see later with the excitable or motor 

 area ; and the striated area of the calcarine fissure (field 17) in the 

 occipital region (Fig. 270), characterised by increase of the cellular 

 layers and the presence of large numbers of small cells, which 

 includes the visual zone. 



III. The effects of complete destruction of the telencephalon in 

 different classes of vertebrates, as discussed in the last chapter, 

 showed that the view of those authors who maintain that all the 

 functions and acts of conscious psychical life are localised ex- 

 clusively in this chief segment of the brain has not been confirmed, 

 nor can it be confirmed by the physiological methods at our dis- 

 posal. There is, however, no doubt that the fore-brain is the seat 

 of all the higher mental activities, particularly the formation of 

 images, their association and calling-up in memory, and their 

 expression in complex voluntary acts in a word, the highest 

 phenomena of the intellect. 



A critical review of the theories that have prevailed as to the 

 material mechanism and seat of psychical phenomena was published 

 by Soury (1899), from a wide point of view, and with great wealth 

 of detail. To use the author's happy expression, it comprises the 

 natural history of the human mind, and could not therefore 

 possibly be summarised in the limits of the present volume. 

 Enough to say that from Alcmeon of Croton (500 B.C.), who seems 

 to have been the first who looked on the brain as the central organ 

 of the soul, to Franz Joseph Gall (1810-18), who first conceived 

 the brain as a collection of organs corresponding to different 

 mental faculties, innumerable hypotheses have been formulated to 

 account for the intimate relations between physiological function 

 and psychical activity i.e. between body and soul. Of these 

 hypotheses, both in classical and in modern times, that which 

 regards the brain, or a part of it, as the material substrate 

 necessary to the activity of the mind, has certainly predominated. 

 This theory, however, only reached its complete expression with 

 Gall. 



Haller (1708-77) regarded the white matter of the brain, not j 

 the grey cortex, which he thought insensitive to stimuli, as the | 

 seat of sensation and the source of movement. He did not allow 

 that different psychical functions could be assigned to particular 

 provinces of the brain, because the nerves of the sense organs are 

 connected with different points of the brain, and have no special 

 seat in the sensorium commune, that is in the white brain matter. 



